Here only a brief overview of factors that may alter or bias any association between gastrointestinal symptoms and diabetes will be discussed.
Disordered motor function
In patients with long-standing type 1 and type 2 diabetes, the prevalence of delayed gastric emptying of a nutrient meal is reported to range from 27% to 40% and the prevalence is similar in insulin-dependent and non-insulindependent diabetes mellitus. In a minority of patients (less than 10%) with long-standing diabetes, gastric emptying is accelerated. In newly diagnosed patients with type 2 diabetes, gastric emptying of carbohydrates has been reported to be accelerated, although others have not confirmed these findings. On the other hand, no data exist on the prevalence of deranged gastric emptying in patients with newly diagnosed type 1 diabetes. Manometric abnormalities were found in 81 of 84 patients with either type 1 or type 2 diabetes who completed a 3 hour fast and 2 hour postprandial motility evaluation. Although some have suggested a link between gastric motor disorder and symptoms, most have not found a strong correlation between symptoms and either delayed or accelerated gastric emptying.
Hence, this is a weak predictor of symptom status overall.
Delayed small bowel and colonic transit have also been reported in 20 – 70% of patients with long-standing diabetes mellitus. However, while no gastrointestinal symptoms correlated with delayed small intestinal transit, constipation (defined as less than three bowel movements/week) was significantly associated with delayed colonic transit.